Automated dispenser with sensor arrangement

ABSTRACT

An automatic electrically powered dispenser for dispensing a product stored in the dispenser includes an active IR sensor system for detecting a user. The IR sensor system includes at least one IR emitter and at least one IR receiver. The IR sensing system is arranged to scan for the presence of a possible user at a certain scanning rate. A sensor control system supplies the active IR emitter(s) with a first current which is constant during one or more single scans and is altered to a different, second current for further scanning. The first and second currents are determined on the basis of a signal strength of the average received IR which is received by the IR receiver(s) during a number of previous single scans. In a simplified system, the average value of the most recently received IR values may be compared to a standard value set in the control system to alter the current supplied to the IR emitter(s).

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of international application PCT/EP2005/007616filed on 13 Jul. 2005, which designated the United States of America.

FIELD OF THE INVENTION

The present invention relates generally to a dispenser having an activeinfrared (IR) sensor system, in particular for dispensers of the typeincluding a motor-driven dispensing system combined with controlcircuitry for sensing the presence of a possible user by means of saidIR sensor system and controlling operation of said motor to effectdispensing of material.

The invention furthermore relates particularly to an automatic toweldispenser (preferably with paper towels stored inside the dispenserhousing) of the electrically powered type, preferably a battery poweredtype (but which could also be AC powered or powered by a combination ofAC and DC power supplies), in which the IR sensor system is used tocontrol dispensing of products such as paper sheets (e.g. paperhand-towels) when the presence of a possible/potential user is detectedto be within a specified zone, without physical contact of the user withthe dispenser (or the sensors) being required for initiating thedispensing sequence.

BACKGROUND TO THE INVENTION

Dispensers of the aforementioned type are known for example from U.S.Pat. No. 6,695,246.

In for example the dispenser according to U.S. Pat. No. 6,695,246, thesensor control circuitry uses active IR (i.e. both IR emission anddetection) to control sensing of the presence of a possible user. The IRis emitted in pulses. In the active IR mode, the presence of an object(i.e. a possible user) can be detected within a detection zone of about12 to 24 cm from the dispenser and upon said detection operates a motorto dispense a hand towel to a user. One IR receiver and one IR emitterare located behind a front cover of the dispenser and each is mounted ina respective tube, the tubes being placed adjacent one another. By thisarrangement the detection distance is kept short (between about 12 to 24cm) so that objects which are outside the detection zone do not lead toundesired and unintentional dispensing. Likewise the object must be inthe correct position and at a correct angle otherwise the tubes willprevent IR from being reflected back and collected by the receiver.Thus, while the possibility of undesirable reflections from othersurfaces or the like is reduced, the sensor system requires fairlyaccurate positioning of the hand to effect operation. When an object isdetected, the microprocessor activates the motor to dispense a towel iftwo scans with sufficient reflected IR are received the IR sensingcontrol system. In order to operate the motor, the IR sensor system usesa background light level reference circuit which provides a referencevoltage V_(B), related to the level of background light and againstwhich a voltage V_(A) from the IR sensor is compared. When voltage V_(A)is greater than voltage V_(B) the motor may operate to dispense a handtowel. This provides an automatic compensation of background light levelso that the signal picked up by the IR receiver must be raised to ahigher level in order that a user is detected.

In the aforementioned dispenser, although a certain degree ofcompensation is made for background light levels which can take accountof some conditions, problems will arise in such a device due totemporary effects of high IR changes due to atmospheric conditions, inparticular when background IR is very low, since only very small changesin reflected IR can cause dispensing to occur even when not required.

Likewise, the problem would also be encountered that as background IRlevels generally increase to a high level, a user's hand becomes harderto distinguish against the background IR because the increased level ofIR due to the IR reflection from a user's hand, when the hand is infront of the dispenser, may be approximately at the same level as thebackground IR, or due to the temporary blocking of the high levelbackground IR, the presence of a hand can even reduce the level to belowthat of background IR received in the IR sensor, such that the hand inmany cases is not reliably detected.

Also, a user's hand which is not detected or is not correctly positionedwith respect to the small area of detection of the sensors on thedispenser, i.e. in the small range of area detected and thus which doesnot immediately activate hand towel dispensing, will often be tempted totouch the dispenser to try and cause dispensing in the belief thattouching of the casing close to the sensors is required, despite anywritten notices which the dispenser may contain in this regard. This isparticularly the case because the user's hand is already at the heightof the dispenser as in the aforementioned document. This can result inlack of hygiene when several users consecutively touch the dispenser.

Further, while the IR emitted intensity from the emitter is seeminglyconstant in the aforesaid document (apart from possible variations tolow battery voltage), such a construction when relying on battery powerfrom batteries (rather than solar cells) often involves usingunnecessarily high power.

The present invention has as one of its objects, to provide animprovement to the active IR detection to take account of background IRchanges.

A further object is to improve the possibility of better hygiene.

A further object is to minimize power consumption of the device atcertain times by taking into account the background IR level.

Further objects of the invention will be apparent upon reading thisspecification.

SUMMARY OF THE INVENTION

The main object of the invention is achieved by a dispenser having thefeatures defined in the independent claim. Certain preferred features ofthe invention are defined in the dependent claims.

Further features of the invention will be apparent to the reader of thisspecification.

The invention provides a means of improving detection reliability bycompensating for background IR levels of increasing or decreasingintensity by means of varying the current supplied to the IR emitter(s),thereby varying the amount of emitted IR used by the sensing system. Oneway of doing this is when general background IR levels are generallyhigh, the power sent out by the IR emitters is made higher by increasingthe current passed through the IR emitter. Thus, a user approaching thedispenser in bright light conditions will more easily be detected, sincethe amount of reflected IR compared to background IR will be larger thanif no current change had been made. Therefore, the difference betweenreceived IR from reflection off the user's hand compared to backgroundIR will be greater, and thus the user's hand will be readily detected,which is particularly advantageous when the user's hand is less whitedue to the lower IR reflection obtained.

Likewise, in low background IR conditions there is often no need for ahigh current to the emitter, since a user's hand will already give ahigh percentage increase of reflected IR compared to background IR to bedetected. Thus, the current supplied to the emitter(s) can be made lowerwhich also saves power. Similarly, when sudden changes in background IRoccur due to e.g. sunlight entering a room or a light being turned on,the lower current to the sensor means that the relative effect of thesechanges on reflected IR (i.e. that being emitted by the emitter andreflected back to the receiver) compared to background IR will bevirtually undetected. However, when a user approaches the dispenser inlow background IR conditions, the reflected IR increase received by theIR receiver will be high compared to background IR even at the lowcurrent levels.

An alternative, possibly simpler, method which can be used to vary theIR emitter(s) current, rather than by comparing (as above) the values ofreflection to background levels, is to set a so-called “standard value”(a threshold value) in the control circuitry, which is a value of theexpected detected signal strength to be received in normal operatingconditions. The current supplied might be e.g. 5 mA at this standardvalue. If this standard value set in the system is called A1, thenduring operation, the control circuitry (MCU thereof) can be made tocalculate the IR level, A2, from a predetermined number of the mostrecently received IR values (i.e. the moving average of the most recentvalues). If A2>A1 (i.e. the detected reflection moving average signallevel A2 is above the stored standard signal level A1), as calculated inthe MCU for example, the current supplied to the emitter can be reduced,preferably in increments. Conversely, in the case where A2<A1, then thecurrent supplied to the emitters can be increased, preferablyincrementally.

The sensors in the inventive dispenser are preferably positioned suchthat the IR emitters create a wide and useful IR detection zone and theIR detectors (i.e. IR receivers) are arranged to prevent IR from theemitters directly entering the receivers and also to reduce IRreflections from other directions.

Any locations on the dispenser or sensors etc., are defined with respectto the dispenser in its normal position of use and not mounted upsidedown or the like. Thus, the lower part of the dispenser is intended tobe at the bottom. Likewise, the lateral direction of the dispenser is ina generally horizontal direction.

Where a vertical direction or plane is referred to, this is normallyintended to refer to the generally vertical direction. When thedispenser is mounted on a true vertical wall (as will be described laterwith reference to FIG. 2 for example), the vertical direction is thus atrue vertical direction. If however, the wall is slightly inclined by afew degrees, a vertical direction referred to with respect to thedispenser will also be inclined by the same amount and in the samedirection as the wall inclination.

Partly due to the good coverage of the sensor system which can detectpotential (possible) users at a sufficient distance from a large rangeof the normal positions of approach to the dispenser, and due to thecompensatory current that is applied to allow better detection, thisallows the system to react to a user's presence early, and thus enablesthe dispenser to be designed to consume low power. This reduced powerconsumption is possible since in periods when a possible user (i.e. anobject assumed to be a user requiring dispensing of a product such as alength of hand towel or toilet paper) is not located near the dispenser,the scanning rate, in addition to the lower current supplied to theemitters, can also be lowered, without any appreciable risk that thescanning rate will be too low to react quickly enough when a productshould be dispensed by a user being detected. When the user is detected,the scanning rate is thus changed to a faster rate.

Low power consumption is particularly important in dispensers which areentirely battery powered by a battery or batteries, which are generallyexpected to operate for a long time (e.g. enough time to dispense 60 ormore rolls of paper without requiring battery replacement) and theimproved arrangement of sensors and the sensing control system allowsless power to be used at times when no users are present requiring aproduct to be dispensed.

The scanning rate, i.e. the number of scans performed per second, ismade to vary upon the location of a user with respect to the dispenser,such that the dispenser operates at a first scanning rate (i.e. performsa scanning sequence by activating IR receiver and emitter circuits, andthen emitting scanning pulses at a first number of single scans, i.e.pulses, per second) when no possible/potential user is detected. Thesystem then increases the scanning rate when a user is considered to beclose to the dispenser (i.e. has entered a “first” detection zone). Thisvariable scanning rate allows very low power to be used when no usersare adequately close to the dispenser, since each scan requires acertain amount of power and the number of scans per second can bereduced, and only to use a higher power level (more scans per second)when required, so that a quick reaction time to dispense a product isexperienced by the user.

The dispenser sensing system may be further improved to reduce powerconsumption, by providing an additional remote sensor linked by either awire connection to the dispenser or by a wireless link (e.g. IR orradio) to the dispenser. This additional sensor can be used to detecte.g. a user entering a washroom in which the dispenser is placed at adifferent location to the entrance and thus can cause the first scanningrate to change to the second scanning rate. Such a “remote” sensorcould, if desired alternatively be mounted on the front-facing portionof the dispenser and could be arranged to operate at a very slowscanning rate due to the distance of the entry to a washroom from thelocation of the dispenser, such that by the time the possible userwishes to use a dispenser and has thus moved closer to the dispenser,the dispenser is already operating at a higher second scanning rateallowing rapid detection by the active IR sensor system of the dispenserdefined in the claims.

Alternatively, the same set of active IR sensors as defined in theclaims which are used to cause the dispenser to dispense a product upondetection of a possible user, can also be used to detect a user enteringa first detection zone. In this way, a user approaching the dispenser(e.g. 40 to 50 cm or perhaps further away from the dispenser) willactivate the sensor system to change the scanning rate to a higherscanning rate and as the user continues to move his/her hands and/orbody closer to the discharge outlet of the dispenser, the user will bedetected as being in a “dispensing zone” and will thus cause thedispenser to dispense a product (e.g. a paper hand towel or paper toilettoil).

If desired, more than two scanning rates can be used. For example afirst slow scanning rate can be used (such as 1 or 2 times per second),followed by a higher second scanning rate (at e.g. 3 to 6 times persecond), followed by a further higher rate (e.g. 7 to 12 times persecond), whereby the scanning rate is increased from one rate to thenext as the user is detected to be moving closer to the dispenser. Thiscan be performed by a series of different sensors for example, eachdetecting at different distances, with the final sensor system being asdefined in the appended claims, or for example by arranging the same setof sensors to detect an increased IR signal reflection from the user asthe user comes closer to the dispenser.

When a user moves away from the dispenser, the scanning rate can then bedecreased again to a lower rate, thereby consuming less sensor operationpower.

As will be apparent, even at relatively short distances for the firstdetection zone (e.g. up to about 50 cm from the dispenser for example atan angle of about 10° to about 45°, or about 30 to about 60°, to thevertical plane slanted in a forward direction away from the rear of thedispenser and downward), the system has significant power savingadvantages while still allowing a good reaction time to dispense atowel.

This is because the user expects to move his/her hands relatively closeto the device in order for dispensing to occur and this takes of theorder of between a quarter and half a second at normal hand movementspeeds (between 0.2 m/s and 0.5 m/s), by which time the dispenser can bemade to be already scanning at the second higher rate (or even a stillhigher rate) and thus be able to dispense very close to the time whenthe hands are in an “expected” position for dispensing (i.e. a positionat which the user would expect a towel to be dispensed, typically some15 to 25 cm from the dispenser outlet).

Likewise, it is preferred that when using the IR sensor system, thesensor system should preferably be able to cope with singular anomaliesof short term high IR reflections as sometimes occurs which might not becompensated purely by the current level currently being applied to theemitter, without dispensing a towel, so that it is appropriate to sensetwo or more consecutive scans, or e.g. a predetermined number of scansin a number of consecutive scans (e.g. two out of three consecutivescans), each being at a predetermined level of IR above background IRlevel, before dispensing a product.

Advantageous use can be made of the varied scanning rate by making thefirst scanning rate between e.g. 0.15 and 0.25 seconds between scans(i.e. the scanning rate when a possible user is outside the firstdetection zone) or even longer (such as between 0.25 seconds and 0.5seconds), and the second scanning rate of the order of about 0.08 to0.12 seconds between scans and requiring only two consecutive scans (ore.g. two out of three consecutive scans) providing a reflected IR levelabove background IR level to activate dispensing. Such dispensing willbe perceived as almost immediate, yet a significant amount of power usedby the sensor system can be saved due to the initial low scanning ratewhich consumes less power.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail with reference tocertain non-limiting embodiments thereof and with the aid of theaccompanying drawings, in which:

FIG. 1 shows a schematic front view of a paper towel dispenser,depicting a schematic view of a first detection zone,

FIG. 2 shows a side view of the arrangement in FIG. 1 whereby a sidepanel of the dispenser has been removed to show schematic details of thepaper roll and paper transport mechanism,

FIG. 3A is a sectional enlarged view, showing further detail than, andtaken through, the lower part of the casing shown in FIG. 1, also fromthe front and at the location of the IR sensors,

FIG. 3B is a schematic diagram of a frontal view of the arrangementshown in FIG. 3A, depicting the approximate frontal view of the firstdetection zone achieved by the active IR sensor arrangement,

FIG. 4 shows an exemplary plot of emittance amplitude of the scanningpulses against time,

FIG. 5 shows a plot of received signal level against time, for a seriesof received IR reflections occurring due to the emitted IR pulses inFIG. 4,

FIG. 6 shows a block diagram of the basic system elements of anembodiment of a dispenser according to the invention,

FIG. 7 shows an RC circuit used for effecting wake-up of themicroprocessor in the MCU so as to perform a scan,

FIG. 8 shows an alternative version of the RC circuit depicted in FIG.7,

FIG. 9 shows an embodiment using a further sensor, additional to themain active IR sensor system, able to detect a user at a furtherdistance from the dispenser,

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 and FIG. 2 show a dispenser 1 in front and side viewsrespectively, whereby FIG. 2 shows the dispenser 1 attached at its rearside to a wall W (the means of attachment are not shown but may be ofany suitable type such as screws, adhesive, or other attachment means),whereby the rear surface of the dispenser lies against said wall W whichis normally vertical.

The dispenser 1 comprises a housing 2, within which is located a productsupply, in this case a supply of paper in a roll 3. The roll 3 issuitably a roll of continuous non-perforated paper, but may alsocomprise perforated paper. Also located in the housing 2 is a papertransport mechanism 4 preferably in the form of a modular drive cassettewith its own casing 15, which can preferably be removed as a single unitfrom the housing 2 when the housing is opened.

FIG. 1 shows the paper roll 3 and the transport mechanism 4 which feedspaper from the roll towards a discharge outlet (see further descriptionbelow), as simple blocks for the sake of simplicity. Likewise FIG. 2shows the paper roll 3 and the transport mechanism 4 in a vastlysimplified form, whereby the transport mechanism includes a drive roller5 engaged with a counter roller 6, whereby a portion of the paper sheet7 is shown located between said rollers 5, 6, with the leading edge ofsaid paper sheet 7 ready to be dispensed at a discharge outlet 8 formedin the housing 2 at the lower side thereof.

The drive roller 5 is shown schematically connected to an electricaldrive motor M powered by batteries B. A gearing, typically in a gearbox,may be included between the motor drive shaft and the drive roller 5.Suitable batteries may supply a total of 6V when new and typically four1.5V batteries are suitable for this purpose. Exemplary of suitabletypes are Duracell's MN1300 batteries, whereby each battery has acapacity of 13 Ah, and which can operate from full to total dischargebetween the range of 1.5V to 0.8V. Operation of the motor M causes driveroller 5 to rotate and to thereby pull paper sheet 7 from the paper roll3 by pinching the paper between the nip of the rollers 5 and 6. Uponactuation, the motor rotates thereby withdrawing paper sheet from theroll 3, which also rotates so as to allow paper to be moved towards thedischarge opening 8. Other forms of drive mechanisms for withdrawingpaper from a roll may also be used. The details of the paper transportmechanism or other product transport mechanism are however not importantfor an understanding of the invention. Such devices are also well knownper se in the art.

It will also be understood from the foregoing that drive roller 5 andcounter roller 6 may have their functions swapped such that the counterroller 6 could be the drive roller which is operably connected to thedrive motor (and thus the drive roller 5 depicted in FIG. 2 only acts asa counter roller in contact with roller 6, normally with paper or towelin the nip therebetween).

Although the principle of operation is explained using paper in the formof a continuous paper sheet in a roll, it is to be understood that thedispenser may be used to dispense other products from a product supply,such as a continuous piece of paper in concertina format for example.Alternative products may be dispensed by the device with appropriateredesign thereof. It is also possible that other dispensing devices aretagged on to the dispenser. For example the dispenser may furtherinclude an air freshener which is activated for example once every 5 or10 minutes (or other suitable time) or once upon a certain number oftowels dispensed. This extra tagged-on dispenser can be controlled bythe dispenser control circuitry (to be described below) or by separatecontrol circuitry (not described herein).

The motor M is at rest and without power applied to it when no paper isto be dispensed. The motor M is rotated when paper is to be dispensedthrough the discharge opening 8. The operation of the motor M iscontrolled by a master control unit (not shown in FIGS. 1 and 2, butdescribed below) connected to a sensing system comprising sensors 9-13,of which sensors 10 and 12 are emitters, preferably IR emitters, andsensors 9, 11, and 13 are IR receivers. Such IR emitters and receiversare well known in the art and typically comprise diode structures.Suitable IR emitters and receivers are for example made by Lite-ONElectronics Inc., under Type number LTE-3279K for the IR emitters andunder Type number LTR-323 DB for the receivers. Other types of IRemitters and receivers may also be used of course. In the shownembodiment, the IR emitters 10, 12 and IR receivers 9, 11, 13, are shownapproximately equally spaced consecutively in the lateral direction X-Xof the housing (generally parallel to the product supply roll 3). Thespacing can suitably be about 5 cm spacing between a consecutive emitterand receiver, such that the distance between sensors 9 and 10, 10 and11, 11 and 12, 12 and 13 are all approximately equal.

The emitters and receivers are shown (see FIG. 2) placed on the rearmostside of the discharge outlet 8. Other arrangements of sensors are alsopossible such as all sensors placed on the front-facing side of theoutlet, preferably in a straight row along the discharge outlet. Thesensors could alternatively be placed on either side of the dischargeoutlet (e.g. emitters on one side and receivers on the other side) andlikewise extend along the discharge outlet. The discharge outlet couldhowever be alternatively placed elsewhere. The arrangement of sensorsshown consecutively in the order receiver/emitter/receiver . . ./emitter/receiver with a correct spacing allows an advantageous shape ofdetection zone 14, which is somewhat tongue-like in shape (see FIGS. 1,2 and 3B). The underlying tongue shape can be altered somewhat dependingon power applied to the emitters and also their extent of protrusionfrom their housing surface and also the extent of recessing of the IRreceivers as well as by their spacing.

With the understanding from this description that a tongue-shapeddetection zone is produced due to the spacing between sensors, to asmall extent by the power supplied, and due to the recessing/protrudingrelationships of the IR emitters and receivers, the skilled person willbe able to readily vary the tongue shape to meet more precise needs ofthe dispenser in any special situation or dispenser size, merely byroutine experimentation.

The dispenser 1, upon detection of a possible user (the detectionprocess being described further below) without any contact of the userwith the dispenser or the sensors, for a sufficient time in the firstdetection zone, determines that a user is present in a dispensing zoneand thus dispenses a product. Dispensing in this case is performed bythe front portion of the paper 7 being discharged automatically throughdischarge opening 8 (i.e. a laterally extending opening, in the lowerpart of the housing, and preferably feeding out downwards). This allowsthe user to grasp the paper 7 and to draw it against a cutting edge suchas cutting edge 16 shown in FIG. 2, proximate the discharge opening 8,so as to remove the torn/cut-off piece of paper. The location of thecutting edge 16 may of course be varied, such as to be at the level of,or up to 1 cm below, and opposite to, the roller 5.

The first detection zone 14 as shown in FIGS. 1, 2 and 3B is shown astongue-like and is inclined downwardly and forwardly of the dischargeopening at an angle x° of preferably between 20° to 30° to the verticalaxis Y. This is achieved by mounting the IR emitters and receivers atbetween 20° and 30° to the vertical plane which extends laterally acrossthe dispenser. The angle at which each of the emitters and receivers isinclined may vary up to a few degrees, but is generally equal for allemitters and receivers so as to produce a better detection zone. Thesensor system is thus able to detect for a vast majority of its fullextent, typically between 10 and 60 cm, in direction Z over an angle ofsome 10° to 45° to the vertical plane (i.e. a detection in a zonesomewhat corresponding to the zone 14 shown in FIG. 2).

Details of one preferred arrangement of emitters and receivers withrespect to the casing will now be explained with respect to FIG. 3A. Theemitters and receivers in this case may suitably be the Lite-ON emittersand receivers described above.

The lower portion of the dispenser comprises a first cover 50 attachedto which is the main PCB (printed circuit board) for the sensors 9-13which are emitters and receivers as described above. To this PCB areattached a series of holders 52 a and 52 b holding each of the sensors.The receiver holders 52 a are shorter than the emitter holders 52 b inorder to provide a means of recessing the receivers 9, 11, 13 more thanthe emitters with respect to a flat planar outer cover 53, which in thecase shown is provided with varying length recesses. Outer cover 53 canbe attached to the emitters and receivers by a frictional fit forexample in the case it is decided to fit these as a single unit,although outer cover 53 may also be attached to the PCB or the firstcover 50 where desired.

As can be seen in FIG. 3A each of the recesses in which the emitters andreceivers are placed are substantially circular. If conical shapedrecesses are provided for example, the extent of protrusion of theactive part of the emitters, and the extent of protrusion of the activepart of the receivers (i.e. for the case that the receivers do indeedprotrude beyond lower surface 54, as is the case shown in FIG. 3A,rather than being totally recessed) may require small adaptations toachieve the desired detection field shape. The relative protrusion ofthe emitters and receivers can be seen by comparing the position of theshort lateral chain line on each sensor which line is either below orabove the (lower) outer surface 54 of outer cover 53. In the case of theemitters 20, 12 which are arranged to have the active emitting portionprotruding outwardly from the outer surface 54 by a larger extent thanthe receivers 9, 11 and 13, the line is shown below the outer surface 54(i.e. outside the outer surface 54), whereas in the case of the activereceiving portion of receivers 9, 11, 13, the lines are above the outersurface 54 because the active receiving portion is at least partiallyrecessed behind the outer surface 54 (it may also be fully recessed suchthat it has no portion thereof protruding outward beyond the surface54).

In the case shown, the distance “A” of the tip of the emitters 10, 12from the surface 54 is approximately 3 mm and the distance “B” of thetips of each of the receivers 9, 11, 13 from the surface 54 is about 1mm. The distances between respective sensors 9-13 is such that x₁approximately equals each of the distances x₂, x₃ and x₄. With therecessed and protruding dimensions of 1 mm and 3 mm respectively, adistance of about 50 mm for each distance x₁, x₂, x₃ and x₄ has beenfound very suitable.

The amount of recessing and protrusion, once the principles of thisinvention are understood, can be determined by routine experimentation.However, a recessing such that the IR receivers project by distance B ofbetween −2 mm (i.e. totally recessed by 2 mm) and +1.5 mm may be used,although a small positive distance B between 0.2 mm and 1.5 mm is mostsuitable. Likewise, for the IR emitters, a protrusion of distance A by 2to 4 mm may be used.

The foregoing configuration of about 3 mm and 1 mm protrusion beyondsurface 54, for the emitters and receivers respectively, produces a veryfavourable tongue shape of the detection zone. The general tongue shapeof the detection zone 14 produced is shown in FIG. 3B (which correspondsto the configuration in FIG. 3A) by the dash-dot chain perimeter line 55indicating the periphery of the area 14. There will be some variation ofthe shape and also the total length of tongue-shaped zone 14 from thedischarge opening 8 in the direction Z (see direction Z in FIG. 2) suchthat it can vary between about 25 cm and about 50 cm, based on applyingvarying power to the emitters between 0.001 mAs and 0.1 mAs in steadyconditions. The depth of the detection zone 14 shown by dimension C inFIG. 2 will however vary little, even when the length of zone 14 changesin direction Z when power is changed. It remains relatively constant forthe arrangement of sensors in the example shown at about 8 cm.

When the current is changed to alter the above range of sensing, it isassumed that a particular range of sensing is required in steady stateconditions, since the current changes defined herein relating to averagereceived IR are however concerned not so much with altering the shape ofthe detection zone 14, but with compensating for background IR whilemaintaining the approximate same size of detection zone.

In FIG. 3B, the ellipses 56, 57, 58, shown below each of the receivers9, 11, 13 are smaller than the ellipses 59, 60 shown below each of theemitters 10, 12. This difference in size is due to the recessed andprotruding nature of these sensors respectively. The ellipses arehowever only a way of diagrammatically representing the principal ofmain field of detection and reception, since practical testing of theexact shape of the detection zone shows that it in fact corresponds toan area 14 bounded by perimeter line 55. A part of a user entering anypart of zone 14 bounded by perimeter 55 can thus be detected by thesystem.

FIG. 3B also shows that a detection blind gap is formed which extends adistance of about 5 cm (with some variation of about 0.5 cm, thusvarying between 4.5 cm and 5.5 cm distance), below the lower surface 54which surface 54 may be substantially at the same vertical level as thedischarge outlet 8. The surface 54 may however be arranged such that itlies 1 to 4 cm above the discharge outlet, thereby however stillproviding an outward surface of the dispenser, such that the intendeddetection field is not blocked in some way by other parts of thedispenser housing.

The blind gap may however be made to have a distance of preferablybetween 4 and 6 cm from the lower surface 54 depending on the relativeprotrusion of the emitters and receivers and their lateral spacing.

The relatively large size of the blind gap is caused largely by therecessing of almost all of the active portion of the receivers behindsurface 54 (i.e. vertically above surface 54 in the position of use).

The blind gap is also shown in FIGS. 1 and 2.

The recessing of the receivers 9, 11, 13 (i.e. their lesser protrusionoutwardly beyond surface 54 compared to the emitters, or their completerecessing entirely above surface 54) is of particular advantage since itsubstantially prevents IR signals emitted from shining directly onto allparts of the receivers which can otherwise degrade system receptionsensitivity. Furthermore, it reduces IR reflection interference fromother directions than the detection zone 14.

This of course assists in providing more reliable sensing, which whencombined with the underlying inventive structure described herein, ofchanging current based on the average background IR, produces a stillbetter result.

As will be explained below in more detail, when a part of a possibleuser's body enters this first detection zone 14, the sensing systemdetects the user's presence and causes the sensor system to change froma first scanning rate to a second scanning rate which is higher thansaid first scanning rate. The sensing system also causes the motor M toturn upon regarding a user (due to the signals received) as beingpresent in a dispensing zone.

This arrangement allows a reliable and accurate IR reception field to beobtained with a shape which is very well suited to the expected handpositioning of a user when the user's hands approach the dispenser.

While a preferred form of the emitter/receiver arrangement as shown inthe Figures has certain advantages, the use of only one emitter and tworeceivers or more than two emitters and three receivers could also beused. Preferably however, to form a desired detection area, there shouldbe one more receiver than emitter when these are arranged consecutivelyas receiver/emitter/receiver etc. Two receivers (one at each lateralend) should preferably be placed proximate the outer lateral ends of thesensor arrangement (and also thereby the dispenser) to allow forreception of IR over the broadest width of the sensor arrangement in thedispenser and thus make the dispenser more user-friendly by creating adesirable detection zone.

In an alternative embodiment shown in FIG. 9, a further sensor 19,remote from the dispenser housing 2 and operatively connected bywireless or wire connection 20 to the sensor system (shown schematicallyat 22) and its control system in the dispenser housing, may be used toform a first detection zone 18 which is further from the dispenser thanthe detection zone 17 (detection zone 17 in this case is similar inshape to the first detection zone 14 in FIGS. 1 and 2). Alternatively oradditionally, a further sensor may be placed on the front part, e.g. afront surface, of the dispenser housing and facing forwards away fromany wall or the like on which the dispenser is mounted, to allow alonger range of detection forwards of the dispenser, such as the sensor21 shown schematically, which is likewise connected to the sensor system22. The sensor 19 and/or 21 may for example be arranged to detect thepresence of possible users up to a distance of more then the firstdetection zone, e.g. a distance of more than 50 cm, preferably more than100 cm, more preferably more than 200 cm, and still more preferably morethan 300 cm or even further from the dispenser housing 2.

The emitters 10, 12 of the sensor system are arranged via suitablecontrol circuitry, which may control circuitry as known per se in theart, to emit pulsed IR at a narrow frequency band of for example about15 kHz ±0.5%. Another IR frequency could however be chosen. Thereceivers 9, 11, 13, are arranged to detect the emitted IR which isreflected against objects (stationary or moving) back towards thereceivers. In order to detect the IR which initiates primarily andalmost entirely from the emitted IR (even up to very strong lightconditions of 10 000 lux or more), rather than all sources andfrequencies of IR radiation due to background influences, the IRreceivers need to be tuned to the frequency of the emitters. Thus, theIR receivers are provided with a detection circuit which suppresses IRoutside the expected frequency range of the reflected waves, andamplifies the IR at the 15 kHz range level. In this regard, while afrequency detection range both above and below the emitted frequencyband range of between 2 to 10 kHz can operate in most situations, it hasbeen found more suitable to use a frequency range (frequency band) whichlies about 3 kHz above and also below the central frequency of theemitted IR. Thus, the receivers are tuned (or in other words“synchronized”) with the emitted IR at a central frequency of 15 kHz byallowing IR in the range of 12 to 18 kHz to be detected (e.g. by use ofa band pass filter set at 12 to 18 kHz). Frequencies outside that bandare thus heavily suppressed, while the frequencies within the 12 to 18kHz band are amplified, with maximum amplification being at the centralfrequency of about 15 kHz up to for example about 53 dB.

By operating with a modulated frequency in the emitters and receivers,the effects of e.g. bright sunlight which might otherwise causesaturation of the IR received signal compared to any reflected signalare substantially obviated allowing the device to work in lightconditions of up to about 10 000 lux background illumination. Thisability to distinguish possible users from other background sources ofIR is also further enhanced by the possibility of supplying a variablecurrent to the IR emitters as disclosed herein.

FIG. 4 shows a series of individual scans (i.e. a pulsed IR emission) ata first scanning rate having a time between individual scans of t1, asecond scanning rate having a time between individual scans of t2 whichis shorter than t1 (i.e. a higher scanning rate than t1) and a thirdscanning rate having a time between individual scan of t3 where t3 isgreater than t1 and t2. The time between individual scans is measured asthe time from the start of one single scan to the time of starting thenext individual scan. Each of the individual scans is here shown ashaving the same pulse intensity (i.e. no adjustment is made betweenindividual scans to take account of previous received reflected scanswhich may result in a different emittance power being supplied to the IRemitters. A further time t4 is shown which is a predetermined time or apredetermined number of pulses separated by time t1 (the first scanningrate) which needs to elapse before the system alters the scanning rateto the third, slowest scanning rate with time interval t3. The pulsewidth of each individual pulse is normally constant.

The time t1 is set at a constant level to lie between 0.15 to 1.0seconds, preferably 0.15 to 0.4 seconds, i.e. such that each individualscan pulse is separated by an equal time t1. The time t1 can however bevaried and a very suitable rate to optimise the device for battery powersaving and reaction time to dispensing has been found to be aboutt1=0.17 seconds. The second scanning rate is always faster than thefirst scanning rate and t2 is set to lie preferably between 0.05 to 0.2seconds, preferably between 0.08 and 0.12 seconds between scans. Thetime t2 can however be varied to be another suitable value, butpreferably lies between 30% to 70% of t1. Time t3 may be set at forexample between 0.3 and 0.6 seconds, although a longer time t3 is alsopossible, such as 1 second or even longer. However for emittance circuittime triggering (In particular by using an RC triggering circuit usingthe RC time constant to cause a discharge of current to themicroprocessor for initiating timing operation) it is most suitable ift3 is set to double the length of t1. Thus t3 may be set at 0.34 secondsin the case when t1 is 0.17 seconds. The initial time t1 can be madevariable, for example via a variable resistor operated from outside thedevice, although typically this will be factory set so as to avoidunintentional alteration of time t1 which is unsuitable in certainsituations.

Time t4 may typically be chosen to be of the order of between 30 secondsto 10 minutes and may also be variably set up in the device dependent onthe type of use and surroundings which are normally encountered wherethe device is to be located. A suitable value for optimised operationhas however been found to be about 300 seconds although may also bemore, where it is desired to save further power.

Although not shown it will be apparent that additional time periods mayalso be set in the device with intermediate time periods (i.e.intermediate between the values of T1 and T2 values, or intermediatebetween t2 and t3 etc) or even greater time periods, dependent onoperating conditions, although the use of three different scanning rateshas been shown to take account of most situations with good performancein terms of reaction time and power saving. For example, a further timeperiod longer than t4, e.g. 30 minutes, occurring during issuing ofscans at interval t3 could be used so as to alter the time periodbetween scans to be longer than t3 (e.g. 10 seconds between individualscans). Such a situation may be useful when the dispenser might nothardly be used for night-time periods. The reason for this will becomeclearer upon reading the following description of operation.

As can be seen in FIG. 4, after four scans S1-S4 at a time interval oft1, the scanning rate changes to the second faster scanning rate withinterval t2 and continues at the second scanning rate for two furtherscans S5 and S6. The reason for this change will be explained below withreference to FIG. 5.

FIG. 5 shows a sample of the possible received signal level (receivedsignal strength) of the received signals R1-R7 caused in response toemitting the scan pulses S1-S7.

The approximate background IR level is indicated as a signal receivedlevel of Q0. This level Q0 may of course vary and as shown further belowthis can however be taken into account in several ways. For simplicityof explanation however, it is assumed in the following example toexplain the basic sensor system operation for detection and scanningalteration, that Q0 remains substantially constant.

When S1 is emitted and there is no object which is not accounted for inthe last background value of received signal, the background levelreceived at R1 will be approximately at level Q0. Likewise at the nextscan S2 the level of IR received is also close to Q0 and thus causes noalteration of the first scanning rate. At scan S3, the received signallevel R3 is however above background level, but only marginally (e.g.less than a predetermined value, for example less than 10%, abovebackground IR level) and thus the first scanning rate is maintained.Such small changes (below the predetermined level) above and below Q0can occur due to temporary changes in moisture levels or persons movingat a longer distance from the dispenser, or stray IR due to changes insunlight conditions or temperature conditions around the dispenser.

At scan S4, the received signal level has reached or surpassed thepredetermined value of e.g. 10% above background IR and the sensorsystem and its control thus assumes that a possible user (e.g. theuser's hands or whole body) is moving closer towards the dispenser inorder to retrieve a product such as a paper towel. In order to be ableto react faster when the user is assumed to wish that a towel to bedispensed (i.e. when the received signal level has reached or surpassedthe predetermined value of e.g. 10% above background IR), the scanningrate thus increases to the second scanning rate and thus issues the nextscanning pulse at a shorter time t2 after the previous pulse.

If the signal level R5 received on the next scan S5 also fulfils thecriteria of being at, or more than, a predetermined level abovebackground IR (e.g. at or greater than 10% above background IR inaccordance with the criteria used for the previous scans) the sensorsystem records via a counter (e.g. in a memory or another form ofregister) a single detection above the predetermined level, and thenissues a further scan S6 at interval t2 to check whether the received IRis still at or above the level of 10% greater than background IR Q0. Asshown in FIG. 5, this is the case for scan S6, and the sensor systemcontrol (comprising both software and a microprocessor in a preferredform) then immediately issues an output to the motor M to start themotor turning in order to dispense a product (e.g. a portion of paper 7from roll 3). In this case, i.e. when two consecutive scans are abovethe predetermined level, the system has thus determined that a possibleuser is in a zone requiring a product to be dispensed and thusdetermines that the user is in a “dispensing” zone.

In the case where only one set of sensors is used to detect the presenceof a user in the first detection zone (e.g. the embodiment of FIGS. 1and 2), the detection zone and the dispensing zone will be the samephysical zone, but it is merely the sensor control system whichlogically determines that a user has entered the dispensing zone.

In the embodiment of FIG. 9 however, where an additional sensor 19and/or 21 is used, the signal level R4 will have been sensed in zone 18and thus will already have caused the first scanning rate to change tothe second scanning rate before the user has entered zone 17 which, inthe case of FIG. 9, would be the dispensing zone which is distinct thefirst detection zone 18. The zones 17 and 18 could of course overlap toa lesser or greater degree, but zone 18 in such a case should alwayshave at least a portion thereof which is arranged to extend further fromthe dispenser than zone 17. In such a case it is however appropriate forthe second scanning rate to be maintained for a time suitable for a userto physically enter the zone 17 (e.g. a time for moving towards a washbasin, washing hands and then using a towel). Such a suitable time maybe set for example between 1 and 10 minutes, during which time thesecond scanning rate is maintained, in the expectation of receiving IRreflected signals R which fulfil the criteria that a product is to bedispensed.

In a further situation, not shown, where the level at R5 is below thepredetermined level (e.g. 10% above background IR), the system may beprogrammed to issue a further scan and to check again whether thereceived signal level is above the predetermined level so as to indicatethat a user is present and wishes to receive a towel. Thus, rather thanalways requiring two consecutive scans to produce two received signalshaving a received signal strength above the predetermined level, it hasbeen found preferable to allow any two of three consecutive scans to beabove the predetermined level. Further possibilities also exist ofcourse whereby the number of scans to allow dispensing of a towel couldbe any two out of four consecutive scans, or any three out of fourconsecutive scans, or further combinations. However, with t1 set at 0.17seconds and t2 at 0.1 seconds, it has been found suitable to allow anytwo out of three consecutive scans to trigger dispensing of a product.

In the case shown in FIG. 4, after a towel or other product has beendispensed (discharged), the system alters the scanning rate back to thefirst scanning rate so as to save power and thus scan S7 is emitted attime t1 after scan S6. Clearly this saves power as early as possible.However, the second scanning rate can however be maintained for longerif desired (situation not depicted in FIG. 4) so that when a user againwishes to take a second or further product (e.g. a further towel) bymoving their hands again towards the dispenser outlet, the dispensingoccurs quickly again.

In the case shown in FIG. 5 however a case is shown corresponding toFIG. 4, where the user has for example torn off a piece of paper whichhas been dispensed from the dispenser, and thus the level of IRradiation received at R7 is below the predetermined level (e.g. a levelof 10% or more above Q0).

The predetermined level above background level at which the sensorsystem control causes discharge of a product to occur has been describedabove as being 10% above background for two out of three consecutivescans. However, practical tests have shown that a more suitable level isat or above 12% greater than background IR, and even more preferably ator above 15% greater than background IR. This is for example to takeaccount of varying light conditions which may occur when a user is closeto the dispenser, but not actually wishing to use it.

However, it has also been found in testing that the increase inreflected IR which is received allows entirely different thresholds tobe used where desired. Thus for example, the sensor circuits can betuned such that the predetermined level above background level is up to90% or more, even up to 95% or more, above background IR, beforedispensing occurs. This allows for example a far greater distinction ofthe reflection from a user's hands compared to any non-desired receivedIR in the pulsed bandwidth of 12 to 18 kHz (e.g. in the case of verystrong light conditions). At the same time, the proximity at which sucha high level occurs is generally less than when a lower predeterminedlevel is used, unless the current to the emitters is slightly increased.

In some rare cases users may move their hands very quickly towards thedispenser and may be aggravated by having to wait for a time more thanabsolutely necessary for the first scanning rate to alter to the secondscanning rate and wait a further 0.2 seconds (when using t2=0.1) eventhough this a negligible time. A further overriding control may thus beincluded in which any single received scan signal at or above e.g. 30%(or a higher amount such as above 95% in the case described in thepreceding paragraph) compared to background level can be used to causeimmediate dispensing of a product, without requiring consecutive scansat or above a predetermined level, even when in the first scanning ratemode. This can also be made to apply in the second scanning rate mode.

After a period of inactivity for an extended time period t4 during whichthe sensing system has been scanning at the first rate, the system canbe allowed to assume that there are no possible users in the vicinity ofthe dispenser. In such a case, even the time t1 may be considered tooshort to allow optimal power saving, and thus the system can alter thescanning rate to the third scanning rate (lower than the first scanningrate), during which a scanning pulse is issued only once after elapse oftime t3. However in such a case, when an IR signal is received which isat or above the predetermined level (e.g. 15% or more above backgroundlevel), then the system should alter the scanning rate directly to thesecond higher scanning rate, rather than first adopting the originalfirst scanning rate. However in such a case, it is appropriate torequire at least two scans but preferably more scans to cause productdispensing. For example, when a washroom where the dispenser is placedis put into darkness, and then at some time later the lights are turnedon, the IR received levels may be considered to determine that a user ispresent. To avoid a product being dispensed in such a case it may beappropriate to let the system have time to take account of thebackground IR levels before being allowed to dispense.

In terms of the background level of IR, as mentioned above, this willvary over time. Likewise, the presence of fixed objects (e.g. soapdishes, other containers, or other fixed objects) within the range ofthe dispenser need to be taken account of as background IR. In order todo this, it has been found suitable to take a moving average of the mostrecently recorded IR received signals R so as to alter the level Q0 on acontinuous basis.

For example, the four (or more or less than four) most recently receivedIR signal values can be used to form the average value of backgroundsignal level by dividing e.g. the sum of the four most recent receivedsignal levels by four for instance. As each new value of IR is received,the oldest value of the four values is moved out of the calculation(e.g. by removing it from a register or store of most recent values inthe control circuitry) and calculating a new average based on the mostrecent values. Calculation of a moving average and the means required todo this in both hardware and/or software for the most recently recordedset of values is very well known in the art of electronics, and thus isdeemed to require no further explanation here.

The predetermined number of previous single scans which is used to formthe (moving) average is typically between two and ten scans, preferablybetween three and six scans, and most preferably four or five scans. Ifthree or less scans are used to form the average of received IR and thisis used when setting the second current to be supplied to theemitter(s), the difficulty may arise that the last values include highIR values due to a hand being present temporarily and then beingremoved, which causes an artificially high average value of received IR.This phenomenon can of course be used, if desired, to advantage insetting the current level to the emitter by comparing the set (e.g.three last consecutive scans) of IR received values which causeddispensing to occur, to the most recent set of IR received values whichdid not cause dispensing to occur. When four or more scans are used thisprovides more stable results for background IR although use of too manyvalues can cause the dispenser not to react quickly enough to backgroundchanges, which thus on some occasions may make the dispenser react moreslowly to the presence of a user.

By using a moving average of background IR level, the further advantageis obtained that when a user who has just withdrawn a towel or otherproduct keeps his/her hands at the dispensing outlet, the received IRlevel will remain high. However, to prevent a user in this way causingdischarge of a large amount of product, e.g. paper towel material, theuser's hands will be regarded as being background IR when they arerelatively stationary and thus dispensing will not occur. To dispense afurther product (e.g. paper), the user must therefore move his/her handsaway from the dispenser sensors to allow a reading of “true” backgroundIR (i.e. background IR without the user's hands being present too closeto the device). Only upon renewed movement of the user's hands towardsthe dispenser sensors can product dispensing be caused to occur again.

A still further means by which misuse of a dispenser by repeatedwithdrawing of towels unnecessarily can be prevented is by arranging, inaddition or even as an alternative to the above moving average, anadjustable minimum elapsed time between towel dispensing (e.g. a time ofbetween 2 and 10 seconds). However this feature is not generallyrequired since in most cases, the inherent elapsed time for the systemto determine a user as being present in the dispensing zone and to turnthe motor to dispense a towel, will be sufficient to prevent suchmisuse.

It will also be appreciated that as the batteries of the dispenserdischarge over time, the power supplied to the sensors may also beaffected which may cause less efficient operation. To prevent this fromoccurring, and thus to ensure a stable voltage is available for supplyto the sensors (until a time close to total battery depletion), aconstant current sink may be employed. Such constant current sinks toprovide voltage stability are well known per se in the art ofelectronics, and thus are deemed to require no further description here,although it will be understood that their use in the sensing circuitryfor such a dispenser as described herein is particularly advantageous.The amount of extra energy required to operate the constant current sinkis negligible, and thus use of such a device is barely noticeable onbattery useable lifetime.

The power supplied to the emitters may additionally be arranged to bevaried by an automatic control, suitably between an amount of 0.001 mAsto 0.1 mAs (using a 6V battery installation), in order to take accountof received reflected signal strength from previous scans, particularlythose resulting in dispensing occurring compared to those which did notcause dispensing (i.e. the latter representing the stable background IR)and to adjust the level of emitted IR to a more suitable level.

This can be achieved by varying the current to the emitters between e.g.1 mA and 100 mA (i.e. a 100-times variation possibility). This can bedone by using the PWM (pulse width modulator) module 106 (to bedescribed later) whereby a square PWM signal is converted to a DCvoltage having an output proportional to the PWM duty cycle, and wherebythe MCU changes the PWM duty cycle to adjust the DC voltage to theemitter circuits, and thus the power of the IR signal emitted, based onsignal strength inputs received by the sensors and sent to the MCU. Forexample, if the reflected signal strength is very low on the last fewscans (e.g. five scans) when dispensing occurred, this may be becausethe typical brightness of the user's hands is low and background lightlevels are relatively high. This may cause received signal levels to beonly just above the predetermined level compared to background IR unlessthe user's hands are placed very close to the sensors, which can lead todifficulty in detection in some circumstances. In such a case it may besuitable to increase the power supplied to the IR emitters so as toreceive a more easily perceptible signal change, i.e. a first current isincreased to a second higher current and this second current applies forthe next scanning pulse (or pulses) which will be sent (unless a furtherchange in background IR is detected which may lead to a further changein current sent to the emitter(s)).

Likewise, if the typical brightness of the user's hands is high andbackground IR levels are low, it may be suitable to decrease the powersupplied to the IR emitters as an easily perceivable signal level change(i.e. reflected IR level during dispensing compared to background IRlevel) is received. In this way, the power supplied to the emitters isstill further optimized to take account of such conditions whileproviding reliable and fast sensing and dispensing. Thus, apart from invery high light conditions, only very low power to the sensors can beused. In this way, it will also be understood that the dispenser can beoptimized such that the first detection zone in which the presence of apossible user causes changing from the first to the second scanning rateis selected to lie at between about 20 and 60 cm, preferably between 25cm and 50 cm from the discharge outlet. It will be apparent that furtherincreases in power to the emitters will increase the range of detection,but the power consumption will increase at a much greater rate and falsedetections may also occur more easily. Thus, the range of up to 50 cmfrom the dispenser for allowing detection of a user is a preferredmaximum for most installations.

When changing the current level from the first to the second current, itmay however be suitable to design the control circuitry such that thefirst and second level of current are held constant for e.g. at leastone second (or even longer) before being allowed to change to adifferent current level.

By altering the supplied current to the emitters in the above mentionedway, the power supplied to the emitters is optimized to take account ofbackground conditions so as to provide a reliable and fast sensing, anddispensing without using unnecessary battery power.

An alternative, possibly simpler, method which can be used to vary theIR emitter current, rather than by comparing (as above) the values ofreflected IR to general background levels, is to set a so-called“standard value” or “threshold value” in the control circuitry, which isa value of the expected detected signal strength received in normaloperating conditions. The current supplied might be e.g. 5 mA. If thisstandard value is called A1, then during operation the control circuitry(MCU thereof) can be made to calculate the IR level, A2, from apredetermined number of the most recently received IR values (i.e. themoving average of the most recent values). If A2>A1 (i.e. the detectedreflection moving average signal level A2 is above the stored standardsignal level A1) the current supplied to the emitter can be reduced,preferably in increments. Conversely, in the case where A2<A1, then thecurrent supplied to the emitters can be increased, preferablyincrementally.

For each single scan the current supplied to the emitter should normallybe kept substantially constant. Thus both for a first current level anda second current level, the current is kept substantially constant atthat respective current level. As will also be clear, there are not onlytwo current levels possible, since as soon as the second current levelis sent in one single scan, that second current level becomes the firstcurrent level for the next scanning and the second current level will bethe next current level to be set (either up or down or unaltered betweeneach scan), all depending on the results of the most recent movingaverage of IR received.

The average received IR is calculated from a predetermined number ofprevious single scans. Preferably, the predetermined number of previoussingle scans refers to the scans which immediately precede the mostrecent scan. A suitable predetermined number of scans may be between 2and 10 scans, preferably between three and six scans, and mostpreferably four or five scans. For calculating the average received IR,the last (e.g. four) single scans are used and the average value of allIR receiver inputs is used for each scan. On the next average IR whichis calculated, the immediately last four single scans are then usedagain (the oldest scan of the previous scans having now been removedfrom the calculation).

A further way of performing a background IR measurement, rather thantaking the average of the previously received IR values which includethe received values of IR reflection from the emitted IR, is to performa reception scan (i.e. activate the receiving circuits for a smallamount of time with the emitters turned off) and measure the level ofincoming IR. This can be performed by the MCU for example. An average ofa predetermined number of the preceding single reception scans can thenbe used to form an average value of received IR (with emitterdeactivated) in the way already described.

In the case of using turned-off emitters to establish background IR, itmay also be suitable to fix a level of received IR (in particular incases where the remaining battery power is very low so that currentlevels supplied to the emitters should not, or cannot, be increasedfurther), which lies for example at about 90% of a received value of IRby the IR receiver when the IR emitter is turned on. Other values e.g.of 85% and upwards could however be chosen. Variations of IR at thisabsolute level of received IR are often too small for accurately beingable to differentiate a change in received IR which is caused due touser presence as compared to external influences and this may lead toincorrect dispensing. Such a situation is more likely to occur indispensers where limited frequency pulsed IR is not used (i.e. oppositeto the foregoing limited 15 kHz frequency emission and the 12-18 kHzdetection system described above) due to the far lower absolute levelsof background IR which are required to saturate the sensor receptionsystem.

It will also be understood that the dispenser can be optimized such thatthe outermost edge of the first detection zone in which the presence ofa possible user causes changing from the first to the second scanningrate, is selected to lie at between about 20 and 60 cm, preferablybetween 25 cm and 50 cm from the discharge outlet. A further increase inpower to the emitters to achieve a longer range will increase the rangeof detection, but the power consumption will increase at a much greaterrate and false detections may also occur more easily despite theadditional measure of emitter current supply level.

In a further preferred embodiment, the dispenser can be arranged to havetwo modes of operation, one being the sensing mode (or “user-sensing”mode) described previously whereby active IR sensing is operating, theother mode being a hanging towel mode whereby each time for example apaper towel is dispensed and also removed (e.g. torn off), a new papertowel is discharged from the dispenser. For this purpose, the cuttingedge 16 as shown in FIG. 2 for example could be mounted such that theapplication of pressure against the cutting edge (often referred to as acutter bar) causes a switch to be actuated to start the motor M to issuea new piece of towel ready to be torn off. The device may also include amanual switch so that this hanging towel mode can be set manually by auser, or automatically set by a timing circuit, for example at knowntime periods when the dispenser will normally be in constant use and theuse of the active IR sensor system is temporarily superfluous.

A hanging towel mode can also for example be suitable in extremely highbackground IR conditions (e.g. above 5000 and preferably above 10000lux) when the IR sensing system is totally saturated and thus cannotdetect the difference in the increased level of IR radiation from a usercompared to background levels, despite any change from the first currentto the second current supplied to the emitters. The dispenser is thusarranged to detect the level of IR radiation against a threshold (i.e. amaximum threshold value), and when said threshold is reached, the sensorcontrol system (i.e. the control system for the sensor system) switchesthe dispensing mode of the dispenser from a user sensing mode (i.e. thecomparison of received IR to background IR for initiating dispensing asdescribed previously) to a hanging towel mode in which a piece of papersheet towel is fed out of the discharge opening 8 and remains hangingthere until it is removed, upon which a further paper towel is fed outof the discharge opening 8 and again remains hanging there.

However, the average received IR detection is preferably stillcalculated during the time that the hanging towel mode is in operationand the control system is arranged to switch back the mode from hangingtowel mode to dispensing mode when the value of average received IRdrops below the threshold value.

Immediate switching back may not always be suitable, since the averageIR may have dropped only temporarily below the threshold and the devicecould be switching constantly between hanging and user sensing modeswhich may confuse a user. Thus, it may be preferable to include a timedelay of a first predetermined time (e.g. five seconds or more, or evenlonger time periods) before switching back to the user-sensing mode.

An even further improvement may be achieved by arranging the controlsystem software (or optionally hardware) to prevent switching back tothe user-sensing mode during the first predetermined time period ifvalue of the average received IR during that time is above the maximumIR threshold. Again, this helps to further smooth out the effects oftemporary background IR changes.

In a dispenser using emitted pulsed IR (e.g. at 15 kHz AC voltage asexplained above) the level of background IR caused in particular bylight (containing all frequencies of IR) at which such a change tohanging towel mode is required will normally be a very high level (e.g.up to or more than 10 000 lux). However, the mode change from usersensing mode to hanging towel mode is particularly advantageous in acheaper type of dispenser system where the IR is not pulsed, but merelya broad frequency band of IR is emitted and a broad frequency band isreceived. In such cases, the level of saturation of receiving side ofthe sensor system occurs at much lower levels of light (e.g. of theorder of 1000 lux). Thus, the switch from user sensing mode to hangingtowel mode would offer a useful addition to such devices withoutincurring the expense of a limited pulsed frequency emission and specialamplifiers and filters on the receiver side.

A further occasion on which it may be useful to switch to hanging towelmode is at a time close to battery depletion, when the power consumptionof the active IR sensing system is unsuitably high for the remainingpower of the batteries (when related to the normal usage to which thedevice is put). In such a case of low battery power, automatic switching(by the dispenser control system including the sensing system) to thehanging towel mode and turning off the emitters used for the sensingmode can be used. Alternatively, the device can be fitted with a lowbattery power warning indicator which could be used by an attendant tomove a manual switch to a hanging towel mode temporarily beforereplacing the batteries.

FIG. 6 shows a block diagram of the basic system of one embodiment of adispenser according to the invention, in which the portion shown indotted lines includes the basic components for IR signal modulation, IRemission and IR reception used to submit a sensing signal to the A/Dmodulation of the master control unit (MCU) which unit contains amicroprocessor.

Box 101 and 102 denote IR emitter(s) and receiver(s) respectivelycorresponding generally to the previously described emitters 10, 12 andreceivers 9, 11, 13 described above. These IR emitters and receivers arepreferably photodiodes. The hand shown outside the dotted linesindicates that IR radiation emitted by the emitter(s) 101 is reflectedby the hand back to receiver(s) 102. Unit 103 is a photo-electricconverter for converting the received IR signal before it is passed tofiltering and amplification unit 104 where the band pass filter andamplification circuits operate to amplify the received signal around thecentral frequency in a limited band width and to thereby suppress otherIR frequencies relatively. The signal is then passed to a signalrectification unit 105, since the IR signal is an AC signal. From theunit 105, the signal passes into the A/D module of the MCU.

The output of the PWM module 106 is controlled by the MCU such that asquare wave signal from the PWM can have its duty cycle varied by theMCU to adjust the DC voltage to the emitter circuits and thus the powerof the IR signal emitted. The PWM 106 is connected to a D/A converter107 and into an IR emitter driving circuitry unit 109 which includes theconstant current sink mentioned previously. Into the same IR emitterdriving circuitry is also fed a signal from a phase frequency detectionmodule 108 which issues a 15 kHz (±0.5%) impulse modulated signal (oranother frequency of modulated signal as considered appropriate) so asto drive the emitters 101 via the emitter driving circuitry 109 to emitmodulated IR signals for short intervals (e.g. each signal is emittedfor about 1 ms). In this regard it should be noted that before themodulated signal is emitted, the MCU should first have already put thefilter and amplification circuit unit 104 for the received signal intooperation for a short period, e.g. 2.5 ms, before emitting a modulatedpulse, so as to allow the receiver circuit to stabilise so as toreliably detect reflected IR from the emitted IR signal. Since the unit104 is already in operation when the IR scanning pulse is emitted, andsince the filters and amplification unit are centered around the centralfrequency of the emitted pulse, there is no need to synchronise thetiming of the emitted pulse and the received pulse to any furtherextent.

The signal from unit 109 feeds into the IR emitter on/off control unit110. The input/output module 118 of the MCU also feeds into the unit 110to be turned on and off as required to thereby perform an IR scan viathe emitter 101.

In order to activate the microprocessor (i.e. wake it up to perform ascan at a certain rate), RC wake-up circuitry 115 feeds into the MCUinto a wake-up detection unit 114. Unit 117 is an external interruptdetection unit.

From the input output module 118 is a feed to unit 119 which can beregarded as the motor driving circuitry which drives the motor M whenthe sensor system (which preferably includes the MCU and software) hasdetected that a product should be dispensed due to the determination ofthe presence of a user in the dispensing zone.

Further peripheral units 111, 112 are respectively a paper sensingcircuit unit and a low power detection circuit (i.e. for detectingbatteries close to depletion). Unit 116 indicates battery power which isused to drive the MCU and also all other peripherals and the motor. Unit120 may be motor overload circuitry which cuts off power to the motorfor example when paper becomes jammed in the dispenser or when there isno paper in the dispenser. Unit 121 is a paper length control unit,which operates such that a constant length of paper (which is itselfvariably adjustable by manual operation e.g. of a variable resistor orthe like) each time the motor is made to operate to dispense a length ofpaper sheet 7 through the discharge opening 8. This unit 121 may alsoinclude a low power compensation module by which the motor under lowerpower is made to turn for a longer period of time in order to dispensethe same length of paper sheet, although the unit may simply be a pulseposition control system whereby the rotation of the motor is counted ina series of pulses and the rotation is stopped only when the exactnumber of pulses has been achieved. Such a pulse position control systemcould include for example a fixedly located photointerruptor which candetect slots in a corresponding slotted unit fixed to the motor driveshaft (or alternatively on the drive roller 5 operably connected to thedrive motor). Unit 122 may be low paper detection circuitry and unit 123may be a unit used to indicate whether the casing is open or closed.This can for example be used to provide automatic feeding of a firstportion of paper from the paper roll through the discharge opening whenthe case is closed, e.g. after refilling with a new roll of paper, sothat the person refilling the dispenser is assured that the device isdispensing properly after having been closed.

Although not shown here, a series of warning or status indication lightsmay be associated for example with various units such as units 111, 112,120 to 123 to indicate particular conditions to a potential user ordispenser attendant or repairman (e.g. if the dispenser motor is jammedor the dispenser needs refilling with paper or the like).

FIG. 7 shows one embodiment of an RC control circuitry which can be usedto give a timed wake-up of the microprocessor in the MCU. The principleof such a circuit is well known and in the present case a suitable valuefor the resistor Re is 820 kOhm and for the capacitor 0.33 microfarads.Although not shown specifically in FIG. 6, the RC wake-up circuitry usesthe input/output unit 118 of the MCU to provide the timed wake-upfunction of the microprocessor so that a scan occurs at the prescribedtime interval (t1, t2 or t3 for example). When there is a high to lowvoltage drop at the input/output, as a result of the RC circuitry, theMCU will “wake-up” and perform a scan. This wake-up leading to theperforming of a scan also requires supporting software. Likewise, thelength of the time t1 and/or t2 and/or t3 can suitably be made as amultiple of the RC circuitry time constant, whereby the input from theRC circuit can be used in the software to determine whether a scan isrequired or not at each interval. In this regard, it will be noted thatan RC circuit is subject to voltage changes at the input (via VDD whichis the MCU supply voltage source acquired after passing through a diodefrom the battery voltage supply). As the voltage of the battery (orbatteries) drops, there will then be an increase in the RC time constantin the circuit of FIG. 7 and thus the times t1, t2 and t3 set initiallywill vary as the batteries become more depleted. For example, with thetime t1 set at the preferred level of 0.17 seconds for a battery levelof 6V, a drop to depletion level of 4.2V will increase time t1 to 0.22s. Thus, the values of t1, t2, t3 etc., as used herein, are to beunderstood as being the values with a fully charged battery source.

FIG. 8 shows a modified RC circuit which has the advantage of using lesscurrent than the circuit shown in FIG. 7. In FIG. 8, three bipolartransistors are used to minimise the current used when the MCU isasleep.

Under normal conditions, the digital circuitry inside the MCU operatesin a logic High voltage state and a logic Low voltage state at which thecurrent drain is very low. However when the RS-wake-up circuitry isconnected as in FIG. 7 (whereby the indication “to MCU” implies aconnection to the input/output port of the MCU) this creates a voltagechange at the input/output port of the MCU which is a progressivevoltage change, due to the charging and discharging process in the RCcircuit. This creates a relatively long working period for the digitalcircuitry in the MCU, in turn resulting in an internally higher currentconsumption in the IC internal circuitry than is present during normaloperation conditions. This results in somewhat higher power consumptionto the MCU during its “off” cycle (i.e. the “sleep” cycle of the MCU).

By the circuitry in FIG. 8, the modification includes the use of twoinput/output ports PA7 (right hand side in the Figure) and PB7 (lefthand side in the Figure) to the MCU. The important aspect of thiscircuit is that two transistors Q2 and Q3 have been added in cascadewhich together modify the RC charge-up characteristics. The MCU PA7 pinthen gives a much sharper charge-up curve. The delay time constant forwaking up the MCU is determined by R4 and C1, which have been givenvalues of 820 kOhm and 0.68 μF respectively in the example shown. Othervalues for other time constants can of course be chosen.

The fast voltage change at port PA7 is achieved after conversion in Q2and Q3, which minimizes the time required for transition from a logicHigh voltage to a logic Low voltage level. Such a circuit as in FIG. 8can achieve about 40% power reduction during the sleep cycle compared tothe FIG. 7 circuitry for approximately the same RC time constants. Thus,the RC timing circuitry of FIG. 8 is particularly advantageous wheremaximum power is to be saved.

1. A dispenser for automatically dispensing a product stored in aproduct supply of said dispenser, said dispenser comprising an electricpower supply and an active IR sensing system, said IR sensor systemincluding at least one IR emitter and at least one IR receiver, whereinsaid IR sensing system is arranged to scan for the presence of apossible user at least at a first scanning rate, and wherein a sensorcontrol system is provided such that said active IR emitter is suppliedwith a first current which is substantially constant during one or moresingle scans but which can be altered to a different, secondsubstantially constant current for further scanning, said first andsecond currents being determined on the basis of a signal strength ofthe average received IR which is received by said at least one IRreceiver during a predetermined number of previous single scans.
 2. Thedispenser according to claim 1, wherein said second current is madehigher than said first current when the average IR received by said IRreceiver increases from a first average received IR to a second higheraverage received IR, and is made lower than said first current when theaverage IR received by said IR receiver decreases from a first averagereceived IR to a second lower average received IR.
 3. The dispenseraccording to claim 1, wherein a first standard value A1 has been set inthe control circuitry, corresponding to a value of the expected detectedsignal strength received in normal operating conditions, and wherein thecontrol system is arranged to calculate a moving average A2 of apredetermined number of the most recently received IR values, and whenA2>A1 the current supplied to the emitter is reduced, and in the casewhere A2<A1, the current supplied to the emitters is increased.
 4. Thedispenser according to claim 1, wherein said predetermined number ofprevious single scans is between two and ten.
 5. The dispenser accordingto claim 1, wherein said first current and said second current can bevaried within fixed maximum and minimum limits.
 6. The dispenseraccording to claim 5, wherein the maximum limit is between 10 and 150greater than said minimum limit.
 7. The dispenser according to claim 1,wherein said sensor system can also scan at a second scanning rate, andwherein said second scanning rate is higher than said first scanningrate, wherein the sensor system is arranged to change said scanning ratefrom said first scanning rate to said second scanning rate uponreceiving a reflected IR level greater than a predetermined value abovebackground IR level for a first predetermined number of single scans,and wherein said sensor system causes a product to be dispensed by saiddispenser when said sensor system detects a change in received IR signalstrength which is at or greater than a predetermined IR signal strengthlevel above a background IR signal strength level for a secondpredetermined number of single scans.
 8. The dispenser according toclaim 7, wherein said predetermined signal strength level is at or above10% higher than background.
 9. The dispenser according to claim 1,wherein said sensor system comprises a plurality of IR receivers and atleast one IR emitter, and the value of received IR values at allreceivers is used to form a single average value of received IR duringone single scan.
 10. The dispenser according to claim 9, wherein saidsensor system comprises at least two IR emitters and at least three IRreceivers, wherein each emitter has one receiver on each lateral sidethereof such that the emitters and receivers are in the orderreceiver-emitter-receiver-emitter-receiver in a lateral direction acrossthe dispenser, and wherein the spacing between each emitter and eachlaterally adjacent receiver is substantially equal.
 11. The dispenseraccording to claim 1, wherein said dispenser comprises a dischargeoutlet on or proximate a lower face thereof, and wherein each of saidemitters and receivers is arranged on said lower face.
 12. The dispenseraccording to claim 1, wherein said dispenser is a paper towel dispenserarranged to both store a supply of paper and to dispense at least aportion of said supply of paper.
 13. The dispenser according to claim 1,wherein said IR emitters are controlled by a sensor control system toprovide IR radiation to a level such that the detection field providedby said emitters is able to detect the presence of a possible user at adistance of up to 25 cm from said discharge outlet.
 14. The dispenseraccording to claim 1, wherein said sensor system is arranged to emit IRradiation only with a first emitting frequency band and wherein saidsensor system is arranged to detect radiation in a limited frequencydetection range, wherein said first emitting frequency is about 15 kHzand said frequency detection range is between about 12 kHz and about 18kHz.
 15. A dispenser according to claim 1, wherein said dispenser is apaper towel dispenser, and the sensor control system is arranged todetect a maximum threshold value of average received IR, upon which saidsensor control system switches a dispensing mode of said dispenser froma user sensing mode to a hanging towel mode.
 16. The dispenser accordingto claim 15, wherein said sensor control system switches said dispensingmode from said hanging towel mode to said user sensing mode when theaverage received IR is measured to lie below said maximum thresholdvalue.
 17. The dispenser according to claim 16, wherein said controlsystem is arranged with a time delay such that when the average receivedIR is measured to lie below said maximum threshold value said switchingoperation from said hanging towel mode to said user sensing mode isdelayed for at least a first predetermined time.
 18. The dispenseraccording to claim 17, wherein said first predetermined time is at leastfive seconds.
 19. The dispenser according to claim 16, wherein saidcontrol system is arranged to prevent switching to said user sensingmode if within said first predetermined time, said maximum thresholdvalue is exceeded.
 20. The dispenser according to claim 1, in which theaverage value of received IR is measured with each IR emitter turnedoff.
 21. The dispenser according to claim 20, wherein the sensor controlsystem is arranged such that when the average value of received IR witheach IR emitter turned off is above 90% of the average value of receivedIR with each IR emitter turned on, said user sensing mode is disabled.22. The dispenser according to claim 21, wherein said control systemswitches to a hanging towel mode after disabling the user sensing mode.23. The dispenser according to claim 21, wherein said control systemswitches from said hanging towel mode back to said user-sensing mode,upon detecting that the average value of received IR with each IRemitter turned off is at or below 90% of the average value of receivedIR with each IR emitter turned on.
 24. The dispenser according to claim1, wherein a constant current sink is used to provide a constant currentto each IR emitter.
 25. The dispenser according to claim 17, whereinsaid control system is arranged to prevent switching to said usersensing mode if within said first predetermined time, said maximumthreshold value is exceeded.